The PARP inhibitor IL-1 signaling pathway is well characterized and it has been shown that IL-1 recruits Myd88 to the IL-1 receptor, which connects

the receptor with a downstream kinase, IRAK [19]. A dominant negative Myd88 inhibits IL-1 induced activation of NF-κB, a major signaling pathway utilized by IL-1 [19]. Importantly, deficiency in Myd88 has been shown to significantly attenuate intestinal polyposis in Apcmin/+ mice and to increase their survival [20], demonstrating that Myd88 dependent signaling critically contributes to intestinal tumorigenesis. Several inflammatory mediators are increased in Apc Min/+ polyps, including IL-1 [20], suggesting that the decreased tumor number in the Apc Min/+ /Myd88−/−compound mouse may be due

to deficient signaling by IL-1. In this study we investigated the pathway whereby macrophages/IL-1 inactivate GSK3β, promote Wnt signaling and enhance growth of colon VS-4718 clinical trial cancer cells. NF-κB has been shown to regulate the survival of tumor cells and to link inflammation and tumor progression [21–23]. We showed that macrophages, like IL-1, activate NF-κB signaling in colon cancer cells, leading to activation of the AKT pathway. PKB/AKT is a kinase that is activated by recruitment to the plasma membrane through phosphorylation on Thr308 by PDK1 and on Ser473 by PDK2 [24, 25]. It has a crucial role in promoting cell survival through phosphorylation of Bad [26], caspase-9 [27], FKHR [28] and IKKα [29]. Another important downstream target of AKT is GSK3β [30], a kinase with a crucial selleck screening library role in Wnt

signaling. The pool of GSK3β that participates in Wnt signaling is present in a multiprotein complex that includes axin, β-catenin and APC [31, 32]. In the absence of Wnt signaling, GSK3β phoshorylates axin, β-catenin and APC, which targets β-catenin for ubiquitin mediated degradation. Wnt signaling results in inactivation of GSK3β, which leads to dephosphorylation of axin, APC and β-catenin [33]. Unphosphorylated β-catenin is stabilized and translocates to Phosphoglycerate kinase the nucleus, where it binds to members of the TCF family of transcription factors, and finally stimulates the expression of target genes such as c-myc, c-jun, CD44 and cox-2 [34]. In this study we established that IL-1 and tumor associated macrophages inactivate GSK3β and promote Wnt signaling in tumor cells through NF-κB dependent activation of PDK1 and AKT. Our data therefore suggest that inhibitors of the NF-κB and PI3K/AKT pathways, which are in development as chemotherapeutic agents, may not only work by inhibiting proliferation and promoting apoptosis of tumor cells, but may also interrupt the crosstalk between the tumor cells and stroma and thereby stall tumor progression.